Therapeutic benefits can be achieved in some instances by providing an active agent to a subject in a manner that extends the time over which the active agent is released. Further, therapeutic benefits can be achieved by providing an active agent to a specific target tissue, instead of systemically. This is because the effect of the agent on the target tissue can be maximized while limiting side effects on other tissues. One approach to providing these benefits is to use a drug polymer delivery system containing an active agent on a medical device. The coating can serve to control the rate at which an active agent is eluted while the fact that it is on a medical device allows the delivery to be in proximity to specific tissues.
Controlling the drug release rate for drug delivery systems is desirable for achieving an effective therapeutic level. Some active agents elute through current drug polymer delivery systems too quickly, others do not elute fast enough. This is partly because active agents are very diverse in their chemical properties including size, hydrophobicity, charge, etc. and these properties affect their interaction with the drug polymer delivery system components and elution medium. For example, small hydrophilic agents such as trigonelline-HCL, diclofenac and chlorhexidine diacetate typically elute with large initial bursts from current drug polymer delivery systems and, therefore, demonstrate poor elution rate control. Bioactive agents can have divergent properties and it can be a challenge to obtain a polymer delivery system that can control both the release of hydrophilic and hydrophobic active agents. A drug delivery polymer system may elute both hydrophilic and hydrophobic drugs at a defined rate, but, often the polymer system is limited by its ability to achieve variations in the release rate.
Therefore, a need exists for a drug polymer delivery system that can provide an effective elution profile with one or more of a variety of active agents.
Two general strategies that have been used to develop improved blood-contacting materials include modifying the chemistry of the bulk material itself, and/or modifying the interfacial properties of the material. With regard to the latter approach, several classes of materials have been covalently bonded onto blood-contacting surfaces with the goal of improving blood compatibility. These include anticoagulants, such as heparin and hirudin; hydrogels; polyethylene oxide (PEO); albumin binding agents; cell membrane components; prostaglandins; and certain polymers. These approaches have met with varying degrees of success in terms of reducing protein adsorption, platelet adhesion and activation, and thrombus formation.
Therefore, a need exists for a coating or material that can provide effective hemocompatibility.